Seaweed Cultivation with a Fishing Boat
12.05.2026
Successful experiment: growing sugar kelp in the Kiel Fjord using fishing equipment
Since 2022, the SpaCeParti project has operated a real-world laboratory in the villages of Stein and Wendtorf. In this research lab, scientists and participating stakeholders collaborate to find solutions for local challenges. One specific motivation is the search for alternative income sources for Baltic Sea fishermen, given the precarious situation of the Baltic Sea fishing industry.
This led to a collaboration between the Rönnau fishing company, Kieler Meeresfarm, and staff from the Center for Ocean and Society. Their goal was to cultivate sugar kelp in Marina Wendtorf for the first time during the winter of 2025–2026. The experiment aimed to determine whether sugar kelp could grow in Wendtorf’s marina, which has a different salt content than Kiel Fjord, and whether it could be deployed and harvested using fishing materials and a fishing boat.
Building on Expertise
Kieler Meeresfarm, in addition to commercial seaweed cultivation, has been growing sugar kelp in the empty berthing boxes of marina harbors during the winter months for several years. As part of their "Hafenalgen" (Harbor Algae) project, they train private individuals in seaweed farming to enable broader participation in the sustainable cultivation of macroalgae in the Baltic Sea. The knowledge and experience gained were shared with the Rönnau fishery, which was also equipped free of charge with approximately 150 meters of seaweed seed lines.
The Experiment
In early November 2025, Rönnau fishery deployed the seed lines provided by Kieler Meeresfarm on four support lines, suspending them below the water’s surface. Recycled fishing materials, such as net rollers, were used for this purpose. Throughout the growth period until the end of March, the growth of the kelp and weather data were documented. By the end of March, the sugar kelp—now up to 25 cm long—was harvested from the support lines using a fishing boat's net hauler, typically used for retrieving gill nets. This method proved highly effective for the kelp lines as well.
The experiment is considered a complete success by all participants. "Growing sugar kelp with our equipment during the winter months is feasible, and if distribution channels open up, it could provide additional income in the winter season."(Leif Rönnau, Fisherman). For this reason, seaweed cultivation will be repeated in the upcoming winter to refine processes and logistics.
The experiment involved Kieler Meeresfarm, Rönnau fishery, Marina Wendtorf, and the Center for Ocean and Society of the research priority area Kiel Marine Science at Kiel University.
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